Discovery of sensorineural hearing loss and ossicle deformity in a Chinese Li nationality family with spondyloepiphyseal dysplasia congenita caused by p.G504S mutation of COL2A1

Background Spondyloepiphyseal dysplasia congenita (SEDC) is an autosomal dominant chondrodysplasia characterized by disproportionate short stature, abnormal epiphyses, and flattened vertebral bodies. COL2A1 has been confirmed as the pathogenic gene. Hearing loss represents an infrequent manifestation for 25–30% of patients with SEDC. The characteristics of the hearing impairment were rarely documented. Methods Audiological, ophthalmic, imaging examinations were conducted on the family members. The whole exome sequencing (WES) was performed to detect the candidate gene, and the Sanger sequencing was used to confirm the causative variation. Results COL2A1 c.1510G>A (p.G504S), a hot spot variation, was identified as the disease-causing mutation of the Chinese Li nationality family with SEDC. This variation was co-segregated with the SEDC phenotype in the family and was absent in the 1000 Genomes Project, ESP and ExAC. Clinically, several manifestations were first demonstrated in SEDC patients caused by p.G504S, including sensorineural hearing loss, auditory ossicles deformity, retinal detachment, sacrum cracked and elbow and wrist joints deformity. Other classical SEDC manifestations such as bones and joints pain, midfacial dysplasia, disproportionate short stature, spinal deformity, thoracocyllosis, coxa arthropathy, myopia and waddling gait were also showed in the family patients. Conclusion We first identified the mutation p.G504S in COL2A1 gene as the pathogenesis in a Chinese Li nationality family and reported the correlation between p.G504S and atypical clinical phenotypes including sensorineural hearing loss, auditory ossicles deformity, retinal detachment, sacrum cracked and elbow and wrist joints deformity. Our findings would extend the phenotypic spectrum of SEDC and deepen clinicians' understanding of genotype–phenotype correlation of the disease.